Physics
posted by Jessica .
Suppose that the magnetic field o fthe Earth were due to a single current moving in a circle of radius 2988 km through the earth’s molten core. The strength of the Earth’s magnetic field on the surface near a magnetic pole is about 6.00E5 T. About how large a current would be required to produce such a field?
I have to use the equation B=((mu_naught*i)/2)* (x^2/(x^2+R^2)^(3/2))
and then for i get:
i=(2*(x^2+R^2)^(3/2))/(mu_naught*R^2)
How do I get x?

At a magnetic pole at the surface, x is the radius of the earth. That is how far you are away from the current loop.